Abstract
In a study of the effectiveness of glove bags to control asbestos exposures to workers and contamination of the environment, a four-man crew removed asbestos in eight rooms in four schools. The workers had little prior experience using glove bags and received on-the-job training in proper techniques during the early stages of the study. Daily personal breathing zone (PBZ) samples on all workers and short-term (STBZ) and work-area samples for airborne asbestos were collected and analyzed by phase contrast microscopy (PCM). The asbestos fiber concentrations of 67 PBZ samples ranged from 0.002 to 1.41 fibers/cc when asbestos lagging was being removed; 67 percent were greater than 0.2 f/cc. During an accidental release, a short-term (15 minute) concentration of 9.3 f/cc was measured. Asbestos concentrations indicated by 77 area samples were slightly lower, ranging from 0.001 to 0.96 f/cc.
For the part of the study that evaluated environmental contamination, various methodologies were used to determine the airborne asbestos concentration for clearance after abatement. Preremoval and postremoval sampling results using aggressive and nonaggressive techniques were analyzed by PCM and transmission electron microscopy (TEM). It was found that aggressive sampling and TEM analysis provided the most sensitive method to evaluate the cleanliness of the work sites that were studied. However, the TEM method has a high inter-laboratory variability, and the polycarbonate filter media used in this study had a highly variable contamination problem. A standard TEM method and a laboratory certification program should be developed to help ensure the reliability of reported TEM results.
Exposure concentrations at these four schools indicate that glove bags, as used during this study, did not completely contain the asbestos being removed. Workers were exposed to airborne asbestos above the National Institute for Occupational Safety and Health recommended exposure limit and the Occupational Safety and Health Administration permissible exposure limit. Asbestos concentrations determined by aggressive sampling and TEM analysis indicated a higher level of contamination after removal than before in five of the eight rooms evaluated. Although worker training and experience are important components in performing proper abatement, this study of glove bags did not provide a basis to specify conditions under which adequate containment can be ensured. Because of the uncertainty in controlling exposures during the use of glove bags, it is essential to provide a back-up containment system (e.g., isolation, barriers, negative air), personal protective equipment (e.g., disposable coveralls), and respiratory protection. Froehlich, P.A.; Hollett, B.A.: Evaluation of Glove Bag Containment and Asbestos Abatement Clearance: Methodologies for Asbestos Removal. Appl. Occup. Environ. Hyg. 8(11):937–944; 1993.